Plating method and apparatus for controlling deposition on predetermined portions of a workpiece

ABSTRACT

The present invention relates to methods and apparatus for plating a conductive material on a workpiece surface in a highly desirable manner. Using a workpiece-surface-influencing device, such as a mask or sweeper, that preferentially contacts the top surface of the workpiece, relative movement between the workpiece and the workpiece-surface-influencing device is established so that an additive in the electrolyte solution disposed on the workpiece and which is adsorbed onto the top surface is removed or otherwise its amount or concentration changed with respect to the additive on the cavity surface of the workpiece. Plating of the conductive material can place prior to, during and after usage of the workpiece-surface-influencing device, particularly after the workpiece surface influencing device no longer contacts any portion of the top surface of the workpiece, to achieve desirable semiconductor structures.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.09/961,193, filed Sep. 20, 2001, now U.S. Pat. No. 6,921.551, which is acontinuation-in-part of U.S. patent application Ser. No. 09/919,788,filed Jul. 31, 2001, now U.S. Pat. No. 6,858,121, which is acontinuation-in-part of U.S. patent application Ser. No. 09/740,701,filed Dec. 18, 2000, now U.S. Pat. No. 6,534,116, which claims a benefitto U.S. Provisional Application No. 60/224,739, filed Aug. 10, 2000. Allof the foregoing applications are hereby incorporated herein byreference in their entireties.

FIELD OF THE INVENTION

The present invention relates generally to an electroplating method andapparatus. More particularly, the present invention is directed to amethod and apparatus that creates a differential between additivesadsorbed on different portions of a workpiece using an externalinfluence and thus either enhance or retard plating of a conductivematerial on these portions

BACKGROUND OF THE INVENTION

There are many steps required in manufacturing multi-level interconnectsfor integrated circuits (IC). Such steps include depositing conductingand insulating materials on a semiconductor wafer or workpiece followedby full or partial removal of these materials using photo-resistpatterning, etching, and the like. After photolithography, patterningand etching steps, the resulting surface is generally non-planar as itcontains many cavities or features such as vias, contact holes, lines,trenches, channels, bond-pads, and the like that come in a wide varietyof dimensions and shapes. These features are typically filled with ahighly conductive material before additional processing steps such asetching and/or chemical mechanical polishing (CMP) is/are performed.Accordingly, a low resistance interconnection structure is formedbetween the various sections of the IC after completing these depositionand removal steps multiple times.

Copper (Cu) and Cu alloys are quickly becoming the preferred materialsfor interconnections in ICs because of their low electrical resistivityand high resistance to electro-migration. Electrodeposition is one ofthe most popular methods for depositing Cu into the features on theworkpiece surface. Therefore the present invention will be described forelectroplating Cu although it is in general applicable forelectroplating any other material. During a Cu electrodepositionprocess, specially formulated plating solutions or electrolytes areused. These solutions or electrolytes contain ionic species of Cu andadditives to control the texture, morphology, and the plating behaviorof the deposited material. Additives are needed to obtain smooth andwell-behaved layers. There are many types of Cu plating solutionformulations, some of which are commercially available. One suchformulation includes Cu-sulfate (CuSO₄) as the copper source (see forexample James Kelly et al., Journal of The Electrochemical Society, Vol.146, pages 2540-2545, (1999)) and includes water, sulfuric acid (H₂SO₄),and a small amount of chloride ions. As is well known, other chemicals,called additives, are generally added to the Cu plating solution toachieve desired properties of the deposited material. These additivesget attached to or chemically or physically adsorbed on the surface ofthe substrate to be coated with Cu and therefore influence the platingthere as we will describe below.

The additives in the Cu plating solution can be classified under severalcategories such as accelerators, suppressors/inhibitors, levelers,brighteners, grain refiners, wetting agents, stress-reducing agents,etc. In many instances, different classifications are often used todescribe similar functions of these additives. Today, solutions used inelectronic applications, particularly in manufacturing ICs, containsimpler two-component additive packages (e.g., see Robert Mikkola andLinlin Chen, “Investigation of the Roles of the Additive Components forSecond Generation Copper Electroplating Chemistries used for AdvancedInterconnect Metallization,” Proceedings of the InternationalInterconnect Technology Conference, pages 117-119, Jun. 5-7, 2000).These formulations are generically known as suppressors andaccelerators. Some recently introduced packages for example Via-Formchemistry marketed by Enthone, Inc. of West Haven, Conn. and Nano-Platechemistry marketed by Shipley, now Rohm and Haas Electronic Materials ofMarlborough, Mass., also include a third component called a leveler.

Suppressors or inhibitors are typically polymers and are believed toattach themselves to the workpiece surface at high current densityregions, thereby forming, in effect, a high resistance film, increasingpolarization there and suppressing the current density and therefore theamount of material deposited thereon. Accelerators, on the other hand,enhance Cu deposition on portions of the workpiece surface where theyare adsorbed, in effect reducing or eliminating the inhibiting functionof the suppressor. Levelers are added in the formulation to avoidformation of bumps or overfill over dense and narrow features as will bedescribed in more detail hereinafter. Chloride ions themselves affectsuppression and acceleration of deposition on various parts of theworkpiece (See Robert Mikkola and Linlin Chen, “Investigation”Proceedings article referenced above). The interplay between all theseadditives in-part determines the nature of the Cu deposit.

The following figures are used to more fully describe a conventionalelectrodeposition method and apparatus. FIG. 1 illustrates across-sectional view of an example workpiece 3 having an insulator 2formed thereon. Using conventional deposition and etching techniques,features such as a dense array of small vias 4 a, 4 b, 4 c and a dualdamascene structure 4 d are formed on the insulator 2 and the workpiece3. In this example, the vias 4 a, 4 b, 4 c are narrow and deep; in otherwords, they have high aspect ratios (i.e., their depth to width ratio islarge). Typically, the widths of the vias 4 a, 4 b, 4 c may besub-micron. The dual-damascene structure 4 d, on the other hand, has awide trench 4 e and a small via 4 f on the bottom. The wide trench 4 ehas a small aspect ratio. In certain embodiments, the trench 4 e has anaspect ratio between about 1:5 and 1:50.

FIGS. 2 a-2 c illustrate a conventional method for filling the featuresof FIG. 1 with Cu. FIG. 2 a illustrates the exemplary workpiece of FIG.1 having various layers disposed thereon. For example, this figureillustrates the workpiece 3 and the insulator 2 having deposited thereona barrier/glue or adhesion layer 5 and a seed layer 6. The barrier/gluelayer 5 may be tantalum, nitrides of tantalum, titanium, tungsten, orTiW, etc., or combinations of any other materials that are commonly usedin this field. The barrier/glue layer 5 is generally deposited using anyof the various sputtering methods, by chemical vapor deposition (CVD),etc. Thereafter, the seed layer 6 is deposited over the barrier/gluelayer 5. The seed layer 6 material may be copper or copper substitutesand may be deposited on the barrier/glue layer 5 using various methodsknown in the field.

In FIG. 2 b, after depositing the seed layer 6, a conductive material 7(e.g., copper layer) is electrodeposited thereon from a suitable platingbath. During this step, an electrical contact is made to the Cu seedlayer and/or the barrier layer so that a cathodic (negative) voltage canbe applied thereto with respect to an anode (not shown). Thereafter, theCu material 7 is electrodeposited over the workpiece surface using thespecially formulated plating solutions, as discussed above. It should benoted that the seed layer is shown as an integral part of the depositedcopper layer 7 in FIG. 2 b. By adjusting the amounts of the additives,such as the chloride ions, suppressor/inhibitor, and the accelerator, itis possible to obtain bottom-up Cu film growth in the small features.

As shown in FIG. 2 b, the Cu material 7 completely fills the vias 4 a, 4b, 4 c, 4 f and is generally conformal in the large trench 4 e. Copperdoes not completely fill the trench 4 e because the additives that areused in the bath formulation are not operative in large features. Forexample, it is believed that the bottom up deposition into the vias andother features with large aspect ratios occurs because thesuppressor/inhibitor molecules attach themselves to the top portion ofeach feature opening to suppress the material growth thereabouts. Thesemolecules cannot effectively diffuse to the bottom surface of the highaspect ratio features such as the vias of FIG. 1 through the narrowopenings. Preferential adsorption of the accelerator on the bottomsurface of the vias, therefore, results in faster growth in that region,resulting in bottom-up growth and the Cu deposit profile as shown inFIG. 2 b. Without the appropriate additives, Cu can grow on the verticalwalls as well as the bottom surface of the high aspect ratio features atthe same rate, thereby causing defects such as seams and voids, as iswell known in the industry.

Adsorption characteristics of the suppressor and accelerator additiveson the inside surfaces of the low aspect-ratio trench 4 e is notexpected to be any different than the adsorption characteristics on thetop surface or the field region 8 of the workpiece. Therefore, the Cuthickness at the bottom surface of the trench 4 e is about the same asthe Cu thickness over the field regions 8. Field region is defined asthe top surface of the insulator in between the features etched into it.

As can be expected, to completely fill the trench 4 e with the Cumaterial 7, further plating is required. FIG. 2 c illustrates theresulting structure after additional Cu plating. In this case, the Cuthickness t3 over the field region 8 is relatively large and there is astep s1 from the field regions 8 to the top of the Cu material 7 in thetrench 4 b. Furthermore, if there is no leveler included in theelectrolyte formulation, the region over the high aspect-ratio vias canhave a thickness t4 that is larger than the thickness t3 near the largefeature. This phenomena is called “overfill” and is believed to be dueto enhanced deposition over the high aspect ratio features resultingfrom the high accelerator concentration in these regions. Apparently,accelerator species that are preferentially adsorbed in the small viasas explained before, stay partially adsorbed even after the features arefilled. For IC applications, the Cu material 7 needs to be subjected toCMP or other material removal process so that the Cu material 7 as wellas the barrier layer 5 in the field regions 8 are removed, therebyleaving the Cu material 7 only within the features as shown in 2 d. Thesituation shown in FIG. 2 d is an ideal result. In reality thesematerial removal processes are known to be quite costly and problematic.A non-planar surface with thick Cu such as the one depicted in FIG. 2 chas many drawbacks. First of all, removal of a thick Cu layer is timeconsuming and costly. Secondly, the non-uniform surface cannot beremoved uniformly and results in dishing defects in large features aswell known in the industry and as shown in FIG. 2 e.

Thus far, much attention has been focused on the development of Cuplating chemistries and plating techniques that yield bottom-up fillingof small features on a workpiece. This is necessary because, asmentioned above, lack of bottom-up filling can cause defects in thesmall features. Recently, levelers have been added into the electrolyteformulations to avoid overfilling over high aspect ratio features. Asbumps or overfill start to form over such features, leveler moleculesare believed to attach themselves over these high current densityregions (i.e., bumps or overfill), and reduce plating there, effectivelyleveling the film surface. Therefore, special bath formulations andpulse plating processes have been developed to obtain bottom-up fillingof the small features and reduction or elimination of the overfillingphenomenon.

A new class of plating techniques called Electrochemical MechanicalDeposition (ECMD) have been developed to deposit planar films overworkpieces with cavities of all shapes, sizes and forms. Methods andapparatus to achieve thin and planar Cu deposits on electronicworkpieces such as semiconductor wafers are invaluable in terms ofprocess efficiency. Such a planar Cu deposit is depicted in FIG. 3. TheCu thickness t5 over the field regions 8 in this example is smaller thanthe traditional case as shown in FIG. 2 c. Removal of the thinner Culayer in FIG. 3 by CMP, etching, electropolishing or other methods wouldbe easier, providing important cost savings. Dishing defects are alsoexpected to be minimal in removing planar layers such as the one shownin FIG. 3.

Recently issued U.S. Pat. No. 6,176,992, entitled “Method and Apparatusfor Electro-Chemical Mechanical Deposition,” commonly owned by theassignee of the present invention, discloses in one aspect a techniquethat achieves deposition of the conductive material into the cavities onthe workpiece surface while minimizing deposition on the field regions.This ECMD process results in planar material deposition.

U.S. patent application Ser. No. 09/740,701, filed on Dec. 18, 2000entitled “Plating Method and Apparatus that Creates a DifferentialBetween Additive Disposed On a Top Surface and a Cavity Surface of aWorkpiece Using an External Influence” now U.S. Patent No. 6,534,116,and assigned to the same assignee as the present invention, describes inone aspect an ECMD method and apparatus that causes a differential inadditives to exist for a period of time between a top surface and acavity surface of a workpiece. While the differential is maintained,power is applied between an anode and the workpiece to cause greaterrelative plating of the cavity surface than the top surface.

Other applications filed that relate to specific improvements in variousaspects of ECMD processes include: U.S. patent application Ser. No.09/511,278, entitled “Pad Designs and Structures for a VersatileMaterials Processing Apparatus,” filed Feb. 23, 2000, now U.S. PatentNo. 6,413,388; U.S. patent application Ser. No. 09/621,969, entitled“Method and Apparatus Employing Pad Designs and Structures with ImprovedFluid Distribution,”filed Jul. 21, 2000, now U.S. Patent No. 6,413,403;U.S. patent application Ser. No. 09/960,236, entitled “Mask PlateDesigns,” filed Sep. 20, 2001, now U.S. Patent No. 7,201,829, whichclaims a benefit to provisional application No. 60/272,791, filed Mar.1, 2001; U.S. patent application Ser. No. 09/671,800, entitled “Methodto Minimize and/or Eliminate Conductive Material Coating Over the TopSurface of a Patterned Substrate and Layer Structure Made Thereby,”filed Sep. 28, 2000, now abandoned; and U.S. patent application Ser. No.09/760,757, entitled “Method and Apparatus for Electrodeposition ofUniform Film with Minimal Edge Exclusion on Substrate,” now U.S. PatentNo. 6,610,190, all of which applications are assigned to the sameassignee as the present invention.

While the above-described ECMD processes provide numerous advantages,further refinements that allow for greater control of materialdeposition in areas corresponding to various cavities, to yield new andnovel conductor structures, are desirable.

SUMMARY

It is an object of the present invention to provide apparatus andmethods that plate a conductive material on a workpiece surface.

It is another object of the present invention to provide apparatus andmethods that plate a conductive material in both small and largefeatures of a workpiece surface with efficiency, cost-savings, andsuperior quality.

It is a further object of the present invention to provide apparatus andmethods for using a workpiece surface influencing device to obtain adifferential between additives disposed on a top surface of a conductivelayer and additives within cavity surfaces of the conductive layer,while minimizing the surface area of the workpiece surface influencingdevice that contacts the top surface of the conductive layer.

It is a further object of the present invention to provide apparatus andmethods for using a workpiece surface influencing device to obtain adifferential between additives disposed on a top surface of a conductivelayer and additives within cavity surfaces of the conductive layer,while minimizing the amount of time that the workpiece surfaceinfluencing device contacts a given area on the top surface of theconductive layer.

It is a further object of the present invention to provide for variousmethods of operating a workpiece surface influencing device along with aplating apparatus to achieve various desirable semiconductor structures.

It is a further object to provide a method of modifying a conventionalplating apparatus to use a workpiece surface influencing device.

The above objects of the invention, among others, taken alone or incombination, are achieved by the present invention, which providesapparatus for, and methods of, plating a conductive material on thesurface of a workpiece.

In one aspect of the invention, an electrolyte solution with at leastone additive disposed therein is applied over the workpiece, such thatthe additive becomes adsorbed onto the top portion and the cavityportion of the workpiece. Using a workpiece surface influencing device,such as a mask or sweeper, that preferentially contacts the top surfaceof the workpiece, relative movement between the workpiece and theworkpiece surface influencing device is established so that the additiveadsorbed onto the top surface is removed or otherwise its amount orconcentration changed with respect to the additive on the cavity surfaceof the workpiece. Plating of the conductive material can place prior to,during and after usage of the workpiece surface influencing device,particularly after the workpiece surface influencing device no longercontacts any portion of the top surface of the workpiece.

In another aspect of the method, the workpiece surface influencingdevice uses a sweeper that directly contacts the top surface of theworkpiece and there is also preferably included a shaping plate locatedbetween the anode and the cathode to assist with providing uniform filmdeposition on the workpiece.

In a further aspect of the invention, a method is disclosed formodifying a conventional plating apparatus with a workpiece surfaceinfluencing device according to the present invention.

In another aspect of the invention, novel semiconductor structures aredescribed.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, advantages and aspects of the present inventionwill become apparent and more readily appreciated from the followingdetailed description of the presently preferred exemplary embodiments ofthe invention taken in conjunction with the accompanying drawings, ofwhich:

FIG. 1 illustrates a cross section of a portion of a workpiece structurewith features therein that requires application of a conductive materialthereover.

FIGS. 2 a-2 c illustrate using various cross sectional views, aconventional method for filling the features of FIG. 1 with a conductor.

FIG. 2 d illustrates a cross sectional view of an ideal workpiecestructure containing the conductor within the features.

FIG. 2 e illustrates a cross sectional view of a typical workpiecestructure containing the conductor within the features.

FIG. 3 illustrates a cross sectional view of a workpiece structureobtained using electrochemical mechanical deposition.

FIG. 4 illustrates a conventional plating apparatus.

FIG. 5 illustrates an electrochemical mechanical deposition apparatusaccording to the present invention.

FIGS. 5 a-5 c, 5 d 1, and 5 d 2 illustrate various sweepers that can beused with the electrochemical mechanical deposition apparatus accordingto the present invention.

FIGS. 6 a-6 e, 6 dd, and 6 ee illustrate using various cross sectionalviews a method for obtaining desirable semiconductor structuresaccording to the present invention.

FIG. 7 illustrates a modified plating apparatus of the presentinvention.

DETAILED DESCRIPTION

The preferred embodiments of the present invention will now be describedwith reference to the following figures. The inventors of the presentinvention have found that by plating the conductive material on theworkpiece surface using the present invention, a more desirable and highquality conductive material can be deposited in the various featurestherein.

The present invention can be used with any workpiece such as asemiconductor wafer, flat panel, magnetic film head, packagingsubstrate, and the like. Further, specific processing parameters such asmaterial, time and pressure, and the like are provided herein, whichspecific parameters are intended to be explanatory rather than limiting.For example, although copper is given as an example of the platedmaterial, any other material can be electroplated using this inventionprovided that the plating solution has at least one of plating enhancingand inhibiting additives in it.

The plating method described herein is a type of ECMD technique where anexternal influence is used on the workpiece surface to influenceadditive adsorption there. The present invention describes a method andapparatus for plating the conductive material onto the workpiece bymoving a workpiece-surface-influencing device, such as a mask or sweeperas described further herein and is positioned between the anode and theworkpiece, to at least intermittently make contact with the varioussurface areas of the workpiece surface to establish an additivedifferential between the top surface and the workpiece cavity features.Once the additive differential is established, power that is appliedbetween an anode and the workpiece will cause plating to occur on theworkpiece surface, typically more predominantly within the cavityfeatures than on the top surface. It should be noted that theworkpiece-surface-influencing device may be applied to the top surfaceat any time before or during plating or the application of power, toestablish an additive differential. The present invention may alsoinclude a shaping plate, as also described further herein. Furthermore,the present invention is directed to novel plating method and apparatusthat provide enhanced electrodeposition of conductive materials into andover the various features on the workpiece surface while reducingplating over others.

Before further discussing the present invention, the distinctions thatare intended to be made herein between a mask (which can also be termeda pad, but will herein be referred to as a mask), a sweeper and ashaping plate will first be described. In applicant's U.S. Pat. No.6,176,992 and U.S. Pat. No. 6,534,116 referenced above, there isdescribed a mask that sweeps the top surface of a workpiece and alsoprovides an opening or openings of some type through, which the flow ofelectrolyte therethrough can be controlled. Applicant has recognizedthat while such a mask as described works very well, that a combinationof two different components, a sweeper and a shaping plate (which canalso be referred to as a diffuser), can alternatively be used, althoughit is noted that a shaping plate can also be used with a mask, though insuch instance there is redundant functionality between the two. It hasalso been found that while having both a sweeper and a shaping plate isdesirable, that the present invention can be practiced using only asweeper. Accordingly, the workpiece-surface-influencing device referredto herein is used to include a mask, a pad, a sweeper, and othervariants thereof that are usable to influence the top surface of theworkpiece more than surfaces that are below the level of the topsurface, such as surfaces within cavity features. It should beunderstood that there are workpiece surface influencing devices otherthan a mask or a sweeper that could potentially be utilized. The presentinvention is not meant to be limited to the specific mask and sweeperdevices described herein, but rather includes any mechanism that throughthe action of sweeping establishes a differential between the additivecontent on the swept and the unswept surfaces of the workpiece. Thisdifferential is such that it causes more material deposition onto theunswept regions (in terms of per unit area) than the swept regions. Thismeans the plating current density is higher on unswept surfaces than onswept surfaces.

FIG. 4 illustrates a conventional Cu plating cell 30 having therein ananode 31, a cathode 32, and an electrolyte 33. It should be noted thatthe plating cell 30 may be any conventional cell and its exact geometryis not a limiting factor in this invention. For example, the anode 31may be placed in a different container in fluid communication with theplating cell 30. Both the anode 31 and the cathode 32 may be verticalthe anode 31 may be over the cathode 32, etc There may also be adiffuser or shaping plate 34 in between the anode 31 and the cathode 32to assist in providing a uniform film deposition on the workpiece. Theshaping plate 34 will typically have asperities 35 that control fluidand electric field distribution over the cathode area to assist inattempting to deposit a globally uniform film.

Other conventional ancillary components can be used along with thepresent invention, but are not necessary to the practice of theinvention. Such components include well known electroplating “thieves”and other means of providing for uniform deposition that may be includedin the overall plating cell design. There may also be filters, bubbleelimination means, anode bags, etc. used for purposes of obtainingdefect free deposits.

The electrolyte 33 is in contact with the top surface of the cathode 32.The cathode 32 in the examples provided herein is a workpiece. Forpurposes of this description, the workpiece will be described as a waferhaving various features on its top surface, and it is understood thatany workpiece having such characteristics can be operated upon by thepresent invention. The. wafer is held by a wafer holder 36. Any type ofwafer holding approaches that allow application of power to theconductive surface of the wafer may be employed. For example, a clampwith electrical contacts holding the wafer at its front circumferentialsurface may be used. Another, and a more preferred method is holding thewafer by vacuum at its back surface exposing the full front surface forplating. One such approach is provided in U.S. patent application Ser.No. 09/960,236, entitled “Mask Plate Design,” filed Sep. 20, 2001, whichclaims a benefit to provisional application No. 60/272,791, filed Mar.1, 2001. When a DC or pulsed voltage, V, is applied between the wafer 32and the anode 31, rendering the wafer mostly cathodic, Cu from theelectrolyte 33 may be deposited on the wafer 32 in a globally uniformmanner. In terms of local uniformity, however, the resulting copper filmtypically looks like the one depicted in FIG. 2 c. In case there isleveling additive(s) in the electrolyte, the thickness t3 may beapproximately equal to the thickness t4 since overfilling phenomenonwould be mostly eliminated by the use of leveler. Power may be appliedto the wafer 32 and the anode 31 in a current-controlled orvoltage-controlled mode. In current-controlled mode, the power supplycontrols the current and lets the voltage vary to support the controlledamount of current through the electrical circuit. In voltage-controlledmode, the power supply controls the voltage, allowing the current toadjust itself according to the resistance in the electrical circuit.

FIG. 5 illustrates a first preferred embodiment of the presentinvention, which can be made not only as a new device, but also bymodifying the conventional plating apparatus such as described above inFIG. 4. In this embodiment of the present invention, a sweeper 40 ispositioned in close proximity to the wafer 32. For simplicity, FIG. 5only shows the shaping plate 34, the wafer 32 and the sweeper 40. Duringprocessing, sweeper 40 makes contact with the top surface of the wafer,sweeping it so that during at least part of the time copper depositionis performed, the additive differential exists. The sweeper 40 may be ofany size and shape and may have a handle 41 that moves the sweeper 40 onthe wafer surface, preferably using programmable control, and can alsobe retractable so that it moves the sweeper 40 entirely off of the areaabove the top surface of the wafer, which will result in even lessinterference than if the sweeper 40 is moved away from the wafer so thatphysical contact between the sweeper 40 and the wafer does not exist, asalso described herein. The handle 41 preferably has a surface area thatis small so as to minimize interference by the handle 41 with platinguniformity The handle may also be coated with an insulating material onits outside surface, or made of a material, that will not interfere withthe process chemistry or the electric fields used during plating.

It is preferable that the sweeper area 42 that makes contact with thewafer surface be small compared to the wafer surface so that it does notappreciably alter the global uniformity of Cu being deposited. There mayalso be small openings through the sweeper and the handle to reducetheir effective areas that may interfere with plating uniformity. Theremay be means of flowing electrolyte through the handle and the sweeperagainst the wafer surface to be able to apply fluid pressure and pushthe sweeper away from the wafer surface when desired. As stated before,sweeper area needs to be small. For example, for a 200 mm diameter waferwith a surface area of approximately 300 cm², the surface area of thesweeper 40 may be less than 50 cm², and is preferably less than 20 cm².In other words in the first preferred embodiment of the presentinvention the sweeper 40 is used to produce an external influence on thewafer surface. The global uniformity of the deposited Cu is determinedand controlled by other means such as the shaping plate 34 that areincluded in the overall design. The sweeping action may be achieved bymoving the sweeper 40, the wafer or both in linear and/or orbitalfashion.

The sweeping motion of the sweeper may be a function of the shape of thesweeper. For example, FIG. 5 a shows an exemplary sweeper 50 on anexemplary wafer 51. The moving mechanism or the handle of the sweeper isnot shown in this figure, and can be implemented using conventionaldrive devices. In a particular embodiment, the wafer 51 is rotatedaround its origin B. As the wafer 51 is rotated, the sweeper 50 isscanned over the surface between the positions A and B in illustrated“x” direction. This way if the velocity of this scan is appropriatelyselected, every point on the wafer surface would be swept by the sweeper50 intermittently. The velocity of the sweeper 50 may be kept constant,or it may be increased towards the center of the wafer 51 to make up forthe lower linear velocity of the wafer surface with respect to thesweeper 50 as the origin B of the wafer rotation is approached. Themotion of the sweeper can be continuous or the sweeper may be movedincrementally over the surface. For example, the sweeper 50 may be movedfrom location A to B at increments of W and it can be kept at eachincremental position for at least one revolution of the rotating waferto assure it sweeps every point on the wafer surface. There may be adevice, such as an ultrasonic transducer, installed in the sweeperstructure that increases the efficiency of the sweeping action and thusestablishes more additive differential during a shorter time period. Thewafer 51, in addition to rotation may also be translated during thesweeping process. While the relative movement preferably occurs ataverage speeds between the range of 1 to 100 cm/s, it is understood thatthe relative movement speed is one variable that can be used to controlthe resulting plating process, with other variables being noted herein.In a modification of this embodiment, the two positions A and B can beat opposite ends of the wafer, in which case the sweeper moves acrossthe diameter of the wafer.

An alternate case involves a stationary wafer and a sweeper that isprogrammed to move over the wafer surface to sweep every point on thatsurface. Many different sweeper motions, both with and without motion ofthe wafer, may be utilized to achieve the desired sweeper action on thewafer surface.

One particularly advantageous sweeper design shown in FIG. 5 b is arotational sweeper 52, which can move around axis 53. In this case, whenthe sweeper 52 is translated on the wafer surface, the wafer may or maynot be moved because the relative motion between the wafer surface andthe sweeper 52 which is necessary for sweeping the wafer surface isprovided by the rotating sweeper. One attractive feature of this designis the fact that this relative motion would be constant everywhere onthe wafer including at the center point B of the wafer. It should benoted that the rotational sweeper 52 may be designed in many differentshapes although the preferred shape is circular as illustrated. Itshould also be noted that more than one circular sweeper may beoperating on the substrate surface.

As shown in FIG. 5 c, the sweeper may also be in the form of a smallrotating sweeping belt 55 (rotating drive mechanism not shown, but beingof conventional drive mechanisms) with a sweeping surface 54 restingagainst the wafer surface. Again, more than one such sweeper may beemployed.

Each of the sweepers illustrated in FIGS. 5 a-5 c can be adapted to beplaced on the end of a handle 41 as described above, such that themotion of the sweeper relative to the workpiece surface can beprogrammably controlled. Further, for embodiments such as thoseillustrated in FIGS. 5 b and 5 c where the sweeper itself is rotatingabout some axis, such as the center of the circular pad in FIG. 5 b andaround the small rollers in FIG. 5 c, this rotation can also beseparately and independently programmably controlled.

Another practical sweeper shape is a thin bar or wiper 58 shown in FIGS.5 d 1 and 5 d 2 being a straight bar 58A and a curved bar 58B,respectively. This bar 58 may be swept over the wafer surface in a givendirection, such as the “x” direction shown in FIG. 5 d 1, underprogrammable control, and, if cylindrical, may also rotate around anaxis. The bar 58 could also be stationery when being used, and, ifdesired, pivotable about a pivot point so that it could be removed fromover the wafer surface when not in use, as shown in FIG. 5 d 2 with bar58B and pivot 59. For each of the sweepers described above, the surfacearea of the sweeper portion of the sweeper that will physically contactthe top surface of the wafer has a size that is substantially less thanthe top surface of the wafer. Typically, the surface area of the sweeperportion that contacts the top surface of the wafer is less than 20% ofthe surface area of the wafer, and preferably less than 10% of thesurface area of the wafer. For the bar or wiper type sweeper, thispercentage is even less.

The body of the sweepers as described above may be made of a compositeof materials, as with the mask described above, with the outer surfacemade of any material that is stable in the plating solution, such aspolycarbonate, TEFLON™, polypropylene, and the like. It is, however,preferable, that at least a portion of the sweeping surface be made of aflexible insulating abrasive material that may be attached on a foambacking to provide uniform and complete physical contact between theworkpiece surface and the sweeping surface. And while the sweepingsurface may be flat or curved, formed in the shape of a circular pad, ora rotating belt, the surface of the sweeper that sweeps the top surfaceof the wafer should preferably be flat in macroscopic scale withmicroscopic roughness allowed to provide for efficient sweeping action.In other words the sweeper surface may have small size protrusions onit. However, if there are protrusions, they preferably should have flatsurfaces, which may require conditioning of the sweeper, much likeconventional CMP pads need to be conditioned. With such a flat surface,the top surface of the wafer is efficiently swept without sweepinginside the cavities.

If the sweeping surface is not flat, which may be the case when softmaterials, such as polymeric foams of various hardness scales are usedas sweeping surfaces, it is noted that the softer the material is, morelikely it will sag into the cavities on the workpiece surface duringsweeping. As a result, the additive differential established between thetop surface and the cavity surfaces will not be as large and processefficiency is lost. Such a softer sweeper material can nevertheless beuseful to fill deep features on a wafer or other type of workpiece inwhich any defects such as scratches on the workpiece surface layer is tobe minimized or avoided. While the soft sweeper cannot efficiently fillthe cavity once the cavity is filled to a level that corresponds to thesag of the soft material, preferential filling can exist until thatpoint is reached. Beyond that point preferential filling of cavities maycease, and plating current may be distributed equally all over thesurface of the wafer.

Referring again to FIG. 5, which could use any of the sweepers asdescribed above, as the sweeper 40 moves over the surface of the wafer32, it influences the additive concentrations adsorbed on the specificsurface areas it touches. This creates a differential between theadditive content on the top surface and within the cavities that are notphysically swept by the sweeper. This differential, in turn, alters theamount of material deposited on the swept areas versus in the cavities.

For example, consider a conventional Cu plating bath containing Cusulfate, water, sulfuric acid, chloride ions and two types of additives(an accelerator and a suppressor). When used together, it is known thatthe suppressor inhibits plating on surfaces it is adsorbed and theaccelerator reduces or eliminates this current or deposition inhibitionaction of the suppressor. Chloride is also reported to interact withthese additives, affecting the performance of suppressing andaccelerating species. When this electrolyte is used in a conventionalplating cell such as the one depicted in FIG. 4, the resulting copperstructure is as shown in FIG. 2 c. If, however, the sweeper 40 starts tosweep the surface of the wafer after conventional plating is carried outinitially to obtain the copper structure shown in FIG. 2 b, the additivecontent on the surface regions is influenced by the sweeping action andvarious Cu film profiles, described hereinafter will result.

FIG. 6 a (which is the same as FIG. 2 b), shows the instant (called timezero herein) sweeper 40 sweeps the top surface areas 60 of the waferthat also has the provided exemplary cavity structure, by moving acrossits top surface in the direction x, preferably at a velocity of 2-50mm/sec and an applied pressure, preferably in the range of 0.1-2 psi.Wafer may also be moving at the same time. It should be noted that thebarrier/glue layer is not shown in some of the figures in thisapplication for the purpose of simplifying the drawings. By mechanicallysweeping the top surface regions 60, the sweeper 40 establishes adifferential between the additives adsorbed on the top surfaces 60 andthe exemplary small cavities 61 and large cavity 62. This differentialis such that there is less current density inhibition in the cavities61, 62 compared to the surface region 60, or in effect current densityenhancement through the cavity surfaces. There may be many differentways the differential in additive content between the swept and unsweptregions of the top surface may give rise to enhanced deposition currentdensity through the unswept surfaces. For example, in the case of aelectroplating bath comprising at least one accelerator and onesuppressor, the sweeper 40 may physically remove at least part of theaccelerator species from the surface areas therefore leaving behind moreof the suppressor species. Or the sweeper may remove at least a portionof both accelerator and suppressor species from the top surface but thesuppressor may adsorb back onto the swept surfaces faster that theaccelerator right after the sweeper is removed from the surface. Anotherpossibility is that activation of the top surfaces by the mechanicalsweeping action may actually play a role in the faster adsorption ofsuppressor species, since it is known that freshly cleaned, in this caseswept, material surfaces are more active than unclean surfaces inattracting adsorbing species. Another possible mechanism that may beemployed in the practice of this invention is using an additive or agroup of additives that when adsorbed on a surface, enhance depositionthere, compared to a surface without adsorbed additives. In this case,the sweeper can be used to sweep away and thus reduce the total amountof additives on the swept surfaces and therefore reduce plating therecompared to the unswept surfaces. It should also be noted that certainadditives may act as accelerators or suppressor depending upon theirchemical environment or other processing conditions such as the pH ofthe solution, the plating current density, other additives in theformulation etc. After the sweeper 40 sweeps the surface 60 at timezero, the sweeper 40 is moved away from the top surface of the wafer,and plating continues on the example cavity structure. However, becauseof the additive differential caused by the sweeper, more plating takesplace into the cavity regions, with no further sweeping action occurringto result in the Cu deposit at a time t1 that is shown in FIG. 6 b.Small bumps or overfill 65 may form over the vias due to the overfillingphenomena discussed earlier. If a leveler is also included in thechemistry these bumps can be avoided, however, as shown hereinafter, thepresent invention can eliminate these bumps without the need of aleveler.

The sweeper 40 is preferably moved away from the surface 60 bymechanical action, although increasing a pressure of the electrolyte onthe sweeper 40, or through a combination thereof can also be used.Increased electrolyte pressure between the sweeper surface and the wafersurface may be achieved by pumping electrolyte through the sweeperagainst the wafer surface. Thus increased pressure then causes thesweeper to hydro-plane and loose physical contact with wafer surface.

Once a differential is established by the sweeper 40 in the additivecontent between the cavity and surface regions, this differential willstart to decrease once the sweeping action is removed because additivespecies will start adsorbing again trying to reach their equilibriumconditions. The present invention is best practiced using additives thatallow keeping this differential as long as possible so that plating cancontinue preferentially into the cavity areas with minimal mechanicaltouching by the sweeper on the wafer surface. The additive packagescontaining accelerator and suppressor species and supplied by companiessuch as Shipley and Enthone allow a differential to exist as long as afew seconds. For example, using a mixture of Enthone ViaForm coppersulfate electrolyte containing about 50 ppm of Cl, 0.5-2 ml/l of VFAAccelerator additive, and 5-15 ml/I of VFS Suppressor additive allowssuch a differential to exist. Other components can also be added forother purposes, such as small quantities of oxidizing species andlevelers. Obviously, the differential becomes smaller and smaller astime passes before the sweeper 40 once again restores the largedifferential.

Let us assume that at time t1 the differential is a fraction of theamount it was when the sweeper 40 just swept the surface area. Thereforeit may be time again to bring the sweeper 40 back and establish theadditive differential. If the sweeper 40 is swept over the surface ofthe copper layer shown in FIG. 6 b, in addition to the new top areas 66,the tops of the bumps 65 which are rich in deposition enhancing specieswill be swept. This action will reduce these species on the top of thebumps, in effect achieving what the leveler additives achieve inconventional plating processes. Continuing sweeping the surface inintervals one can obtain the flat Cu deposition profile shown in FIG. 6c. With respect to the FIG. 6 c profile, it is also noted that thisleveling occurs because the bumps or overfills, and the trough regionstherebetween, provide a similar structure as the top surface portion andcavity portion that requires plating according to the present invention.Accordingly, by creating the additive differential between the overfillsand the trough regions, plating of the trough regions occurs faster thanplating of the overfills, and leveling occurs.

And with a sweeper 40 as described above, since plating on a largeportion of the wafer can occur while another small portion of the waferis being swept, this profile can be achieved with continuous sweepingwithout removing the sweeper 40 from the top surface of the wafer.

Let us now assume that at time t1 the additive differential between thetop regions and within feature is still substantial so that conventionalplating can continue over the copper structure of FIG. 6 b withoutbringing back the sweeper 40. Since the enhanced current density stillexists over the small features and within the large feature, bycontinuing conventional plating over the structure of FIG. 6 b, one canobtain the unique structure of FIG. 6 d, which has excess copper overthe small and large features and a thin copper layer over the fieldareas. Such a structure may be attractive because when such a film isannealed, it will yield large grain size in the features over whichthere is thick copper, which results in lower resistivityinterconnections and better electromigration resistance. This selectiveenhanced deposition is a unique feature of the present invention.Features with enhanced Cu layer are also attractive for the copperremoval step (electroetching, etching or CMP steps), because theunwanted Cu on the field regions can be removed before removing all ofthe excess Cu over the features. Then excess Cu over the features can beremoved efficiently and the planarization can be achieved withoutcausing dishing and erosion defects. In fact, the excess Cu directlyover the features may be removed efficiently by only the barrier removalstep, as explained further hereinafter.

The structure in FIG. 6 e can also be obtained by the present invention.In this case the sweeper 40 is swept over the structure of FIG. 6 b. Asexplained previously, the tips of the bumps 65 in FIG. 6 b are rich incurrent density enhancing or accelerating additive species. In fact thisis the reason why the bumps or overfill regions form. By sweeping thetips of the bumps, the deposition enhancing species near the tips of thebumps are reduced and the growth of the bumps is slowed down. In otherwords the leveling action achieved chemically in the prior art by use ofa leveler in the electrolyte formulation is achieved through the use ofthe mechanical sweeping of the present invention. After sweeping thesurface and the bumps, plating is then continued with further sweepingoccurring only to the extent necessary on the surface of the wafer,depending upon the characteristics of the bumps that are desired. Thisyields a near-flat Cu deposit over the small features and a bump oroverfill over the large feature, as shown. It is apparent that the moresweeping action that occurs, the less pronounced the bumps will become.

It should be noted that the time periods during which the sweeper isused on the surface is a strong function of the additive kinetics, thesweeping efficiency, the plating current and the nature of the Cu layerdesired. For example, if the plating current is increased, thepreferential deposition into areas with additive differential may alsobe increased. The result then would be thicker copper layers over thefeatures in FIGS. 6 d and 6 e. Similarly using additives with kineticproperties that allow the additive differential to last longer can givemore deposition of copper over the unswept features because longerdeposition can be carried out after sweeping and before bringing backthe sweeper. The sweeping efficiency is typically a function of therelative velocity between the sweeper surface and the workpiece surface,the pressure at which sweeping is done, and the nature of the sweepersurface among other process related factors.

FIG. 6 dd schematically shows the profile of the deposit in FIG. 6 dafter an etching, electroetching, CMP or other material removaltechnique is used to remove most of the excess Cu from the surface. Forclarity, the barrier layer 5 is also shown in this figure. As can beseen in FIG. 6 dd, excess Cu from most of the field region is removedleaving bumps of Cu only over the features.

FIG. 6 ee similarly shows the situation after the wafer surface depictedin FIG. 6 e is subjected to a material removal step. In this case thereis a bump of Cu only over the large feature.

In any case removal of the bumps in FIGS. 6 dd and 6 ee and formation ofa planar surface with no dishing can be achieved during the removal ofthe barrier layer 5 from the field regions using techniques such as CMP.The result is the structure shown in FIG. 2 d. Dishing, which isdepicted in FIG. 2 e, is avoided in this process because there is excessCu in the large feature at the beginning of the barrier removal step.

It is possible to use DC, pulsed or AC power supplies for plating tooccur using DC, pulsed, or AC power. Power can be controlled in manymanners, including in a current controlled mode or in a voltagecontrolled mode or a combination thereof. Power can be cut off to thewafer during at least some period of the plating process. Especially ifcutting off power helps establish a larger additive differential, powermay be cut off during a short period when the sweeper sweeps the surfaceof the wafer and then power may be restored and enhanced deposition intothe cavities ensues. Sweeper 40 may quickly sweep the surface at highpace and then retracted for a period of time or it may slowly move overthe surface scanning a small portion at a time in a continuous manner.FIG. 7 is a sketch of an apparatus in accordance with the secondpreferred embodiment of the present invention, which can be made notonly as a new device, but also by modifying the conventional platingapparatus such as described above in FIG. 4. In FIG. 7, a mask 70 isdisposed in close proximity of the wafer 71. A means of applying voltageV between the wafer 71 and an electrode 72 is provided. The mask 70 hasat least one, and typically many, openings 73 in it. The openings 73 aredesigned to assure uniform deposition of copper from the electrolyte 74onto the wafer surface. In other words, in this embodiment the surfaceof the mask 70 facing the wafer surface is used as the sweeper and themask 70 itself also establishes appropriate electrolyte flow andelectric field flow to the wafer surface for globally uniform filmdeposition. Examples of specific mask that can be used are discussed inU.S. patent application Ser. No. 09/960,236. entitled “Mask PlateDesign,” filed Sep. 20, 2001, which claims a benefit to provisionalapplication No. 60/272,791, filed Mar. 1, 2001.

During processing, the mask surface is brought into contact with thesurface of the wafer as the wafer and/or the mask 70 are moved relativeto each other. The surface of the mask 70 serves as the sweeper on thewafer surface and establishes the additive differential between thesurface areas and the cavity surfaces.

For example the mask and wafer surfaces may be brought into contact,preferably at a pressure in the range of 0.1-2 psi, at time zero for ashort period of time, typically for a period of 2 to 20 seconds or untilan additive differential is created between the top surface and thecavity surface. After creating the differential between the additivesdisposed on the top surface portion of the wafer and the cavity surfaceportion of the wafer, as described above, the mask 70 is moved away fromthe wafer surface, preferably at least 0.1 cm, so that plating can occurthereafter. The mask is moved away from the wafer surface by mechanicalaction, increasing a pressure of the electrolyte on the mask, or througha combination thereof. As long as the differential in additives remains,plating can then occur. The plating period is directly related to theadsorption rates of the additives and the end copper structure desired.During this time, since the mask 70 does not contact the top surface ofthe wafer, the electrolyte solution then becomes disposed over theentire workpiece surface, thereby allowing plating to occur. And, due tothe differential, plating will occur more onto unswept regions such aswithin features than on the swept surface of the wafer. Since theelectrolyte is disposed over the entire wafer surface, this also assistsin improving thickness uniformity of the plated layer and washing thesurface of the workpiece off particulates that may have been generatedduring sweeping.

Also, this embodiment advantageously reduces the total time of physicalcontact between the mask 70 and the wafer and minimize possible defectssuch as scratches on the wafer. This embodiment may especially be usefulfor processing wafers with low-k dielectric layers. As well known in theindustry, low-k dielectric materials are mechanically weak compared tothe more traditional dielectric films such as SiO2. Once a sufficientadditive differential no longer exists, the mask 70 can again move tocontact the wafer surface and create the external influence, asdescribed above. If the mask 70 repeatedly contacts the surface of thewafer, continued plating will yield the Cu film of FIG. 6 c.

If a profile as illustrated in FIG. 6 d is desired using thisembodiment, then, in a manner similar to that mentioned above, after aprofile as illustrated by FIG. 6 b is achieved by plating based upon anadditive differential as described above, then a conventional plating,without creating a further additive differential, can be used so thatthe profile illustrated in FIG. 6 d is achieved.

If a profile as illustrated in FIG. 6 e is desired using thisembodiment, then, in a manner similar to that mentioned above, after aprofile as illustrated by FIG. 6 b is achieved by plating based upon anadditive differential as described above, then a combination of platingbased upon an additive differential as described above followed byconventional plating can be used so that the profile illustrated in FIG.6 e is achieved. This is obtained by using the mask to sweep theadditive disposed on the bumps over the small features on the topsurface of the wafer, and therefore slowing the growth of conductor downat those bumps. Accordingly, once the mask is moved away from thesurface, growth continues more rapidly over the large features whoseinside surfaces had not been swept by the mask action. While the FIG. 5embodiment described above was described using a sweeper, and the FIG. 7embodiment was described above using a mask, it is understood that thetwo mechanisms, both being workpiece-surface-influencing devices can beused interchangeably, with our without a shaping plate.

There are other possible interactive additive combinations that can beutilized and other additive species that may be included in the platingbath formulation. The present invention is not meant to be limited tothe example interactive additive combinations cited herein, but ratherincludes any combination that establishes a differential between theadditives on the swept and the unswept surfaces of the wafer. Thisdifferential is such that it causes more material deposition onto theunswept regions (in terms of per unit area) than the swept regions. Thismeans the plating current density is higher on unswept surfaces than onswept surfaces. The sweeper 40 in FIG. 6 a is preferably flat and largeenough so that it does not go or sag into and sweep an inside surface ofthe largest features on the wafer.

Along with using copper and its alloys as the conductive material, manyother conductive materials such as gold, iron, nickel, chromium, indium,lead, tin, lead-tin alloys, nonleaded solderable alloys, silver, zinc,cadmium, ruthenium, their respective alloys may be used in the presentinvention. The present invention is especially suited for theapplications of high performance chip interconnects, packaging,magnetics, flat panels and opto-electronics.

In another embodiment, and of particular usefulness when using a mask ora sweeper for sweeping, it is recognized that the plating current canaffect adsorption characteristics of additives. For some additivesadsorption is stronger on surfaces through which an electrical currentpasses. In such cases, adsorbing species may be more easily removed fromthe surface they were attached to, after electrical current is cut offor reduced from that surface. Loosely bound additives can then beremoved easily by the mask or the sweeper. In the cavities, althoughloosely bound, additives can stay more easily because they do not getinfluenced by the external influence. Once the mask or the sweeper isused to remove loosely bound additives with power cut off, the mask orthe sweeper can be removed from the surface of the wafer, and power thenapplied to obtain plating, with the additive differential existing. Thisway sweeping time may be reduced minimizing physical contact between thesweeper and the wafer surface.

In the previous descriptions, numerous specific details are set forth,such as specific materials, mask designs, pressures, chemicals,processes, etc., to provide a thorough understanding of the presentinvention. However, as one having ordinary skill in the art wouldrecognize, the present invention can be practiced without resorting tothe details specifically set forth.

Although various preferred embodiments have been described in detailabove, those skilled in the art will readily appreciate that manymodifications of the exemplary embodiment are possible withoutmaterially departing from the novel teachings and advantages of thisinvention. It will be appreciated, therefore, that in some instancessome features of the invention will be employed without a correspondinguse of other features without departing from the spirit and scope of theinvention as set forth in the appended claims.

1. A method of electroplating a conductive top surface of a workpiece,the conductive top surface of the workpiece including a top portion anda cavity portion, the conductive top surface defined by a seed layer,the method comprising: applying, over the conductive top surface of theworkpiece, an electrolyte solution with at least one additive disposedtherein, a first portion of the additive becoming adsorbed on the topportion and a second portion of the additive becoming adsorbed on thecavity portion; using a workpiece-surface-influencing device to makephysical contact with the top portion and establishing relative movementwith the workpiece to change at least the first portion of the additiveadsorbed onto the seed layer of the top portion; after making physicalcontact, moving the workpiece-surface-influencing device away from theworkpiece surface so that the physical contact between theworkpiece-surface-influencing device and the workpiece no longer occurs;after moving the workpiece-surface-influencing device away from theworkpiece surface, electroplating the conductive top surface of theworkpiece with a conductor obtained from the electrolyte solution atleast during a period of time when at least some of the change ismaintained and while the workpiece-surface-influencing device remainsmoved away from the workpiece surface, thereby causing greaterelectroplating over the seed layer of the cavity portion relative to theelectroplating over the seed layer of the top portion, wherein theelectroplating results in overfill of the conductor electroplated overthe cavity portion relative to the conductor electroplated over the topportion; and after electroplating, removing a portion of the conductorfrom over the top portion of the workpiece surface and a first portionof the conductor from over the cavity portion, wherein after removal asecond portion of the conductor remains over the cavity portion.
 2. Themethod of claim 1, wherein removing the portion of the conductor overthe top portion comprises removing substantially all of the conductorover the top portion.
 3. The method of claim 1, wherein removingcomprises chemical mechanical polishing.
 4. The method of claim 1,wherein removing comprises electroetching.
 5. The method of claim 1,wherein removing comprises etching.
 6. The method of claim 1, whereinthe conductive top surface further includes a plurality of small cavityportions, wherein the plurality of small cavity portions have widthsthat are smaller than the width of the cavity portion, wherein theelectroplating results in an overfill of the conductor being plated overthe plurality of small cavity portions.
 7. The method of claim 6,wherein the electroplating results in the overfill of the conductorbeing plated over the plurality of small cavity portions is relative tothe conductor electroplated over the top portion.
 8. The method of claim1, further comprising annealing the workpiece before removing theportion of the conductor from over the top portion of the workpiecesurface and the first portion of the conductor from over the cavityportion.
 9. The method of claim 8, wherein, after annealing, a grainsize of the conductor over the cavity portion is greater than a grainsize of the conductor over the top portion.
 10. The method of claim 1,wherein the at least one additive comprises an accelerator.
 11. Themethod of claim 1, wherein the electroplating comprises applying avoltage between the workpiece and an electrode.